Thorium Complexation with Aliphatic and Aromatic Hydroxycarboxylates: A Combined Experimental and Theoretical Study.

Hydroxycarboxylic acids, viz., α-hydroxyisobutyric acid (HIBA) and mandelic acid (MA), have been widely employed as eluents for inner transition metal separation studies. Both extractants have identical functional groups (OH and COOH) with different side-chains.

Additive energy functions have predictable landscape topologies.

Recent work [Mirth et al., J. Chem.

Modulating Aggregation in Microemulsions: The Dispersion by Competitive Intermolecular Interaction Model.

A phenomenological model has been developed for the mechanism of action of phase modifiers as additives that control aggregation phenomena within water-in-oil emulsions. The "Dispersion by Competitive Intermolecular Interaction" model (DCI) explicitly considers the strength and prevalence of different that influence the molecular association of amphiphiles, the resulting distribution of aggregate size, and interaggregate interactions that influence phase phenomena. The existing "cosolvent" and "cosurfactant" association models, which describe the distribution of these amphiphiles within the solution, are re-examined in the context of intermolecular interactions.

Achieving highly efficient and selective cesium extraction using 1,3-di-octyloxycalix[4]arene-crown-6 in -octanol based solvent system: experimental and DFT investigation.

Due to the long half-life of Cs ( ∼ 30 years), the selective extraction of cesium (Cs) from high level liquid waste is of paramount importance in the back end of the nuclear fuel cycle to avoid long term surveillance of high radiotoxic waste. As 1,3-di-octyloxycalix[4]arene-crown-6 (CC6) is suggested to be a promising candidate for selective Cs extraction, the improvement in the Cs extraction efficiency by CC6 has been investigated through the optimization of the effect of dielectric media on the extraction process. The effects of the feed acid (HNO, HCl, and HClO) and the composition of the diluents for the ligand in the organic phase on the extraction efficiency of Cs have been investigated systematically.

Role of O Substitution in Expanded Porphyrins on Uranyl Complexation: Orbital- and Density-Based Analyses.

Search for new U(VI) sequestering macrocyclic ligands is an important area of research due to manifold applications. Besides hard- or soft-donor-based ligands, mixed-donor ligands are also gaining popularity in achieving optimized performances. However, how the combination of hard-soft-donor centers alters the bonding interactions with U(VI) is still not well-understood.

Periodic trends and complexation chemistry of tetravalent actinide ions with a potential actinide decorporation agent 5-LIO(Me-3,2-HOPO): A relativistic density functional theory exploration.

A relativistic density functional theory (DFT) study is reported which aims to understand the complexation chemistry of An ions (An = Th, U, Np, and Pu) with a potential decorporation agent, 5-LIO(Me-3,2-HOPO). The calculations show that the periodic change of the metal binding free energy has an excellent correlation with the ionic radii and such change of ionic radii also leads to the structural modulation of actinide-ligand complexes. The calculated structural and binding parameters agree well with the available experimental data.

Enhancing Actinide(III) over Lanthanide(III) Selectivity through Hard-by-Soft Donor Substitution: Exploitation and Implication of Near-Degeneracy-Driven Covalency.

Soft donor ligands often provide higher selectivity for actinides(III) over chemically similar lanthanides(III), e.g., in the Am-Eu pair.

Thorium decorporation efficacy of rationally-selected biocompatible compounds with relevance to human application.

During civil, nuclear or defense activities, internal contamination of actinides in humans and mitigation of their toxic impacts are of serious concern. Considering the health hazards of thorium (Th) internalization, an attempt was made to examine the potential of ten rationally-selected compounds/formulations to decorporate Th ions from physiological systems. The Th-induced hemolysis assay with human erythrocytes revealed good potential of tiron, silibin (SLB), phytic acid (PA) and Liv.

The coordination chemistry of lanthanide and actinide metal ions with hydroxypyridinone-based decorporation agents: orbital and density based analyses.

In the context of the mitigation of the biological effects of internal radionuclide contamination and for efficient decorporation, the design and development of efficient chelators for lanthanide and actinide metal ions has become a central issue. The pioneering work of Raymond and coworkers (Chem. Rev.

Unusual intramolecular CHO hydrogen bonding interaction between a sterically bulky amide and uranyl oxygen.

The selective separation of toxic heavy metals such as uranyl can be accomplished using ligands with stereognostic hydrogen bonding interactions to the uranyl oxo group, as proposed by Raymond and co-workers (T. S. Franczyk, K.

Divalent ions are potential permeating blockers of the non-selective NaK ion channel: combined QM and MD based investigations.

The bacterial NaK ion channel is distinctly different from other known ion channels due to its inherent non-selective feature. One of the unexplored and rather interesting features is its ability to permeate divalent metal ions (such as Ca and Ba) and not monovalent alkali metal ions. Several intriguing questions about the energetics and structural aspects still remain unanswered.

Speciation of uranium-mandelic acid complexes using electrospray ionization mass spectrometry and density functional theory.

Rationale: Mandelic acid is a complexing agent employed for the liquid chromatographic separation of actinides. However, the types of species and the structural details of the uranyl-mandelate complexes are still unknown. Understanding the nature of these complex species would provide better insight into the mechanism of their separation in liquid chromatography.

Evaluation of an Ultrafast Molecular Rotor, Auramine O, as a Fluorescent Amyloid Marker.

Recently, Auramine O (AuO) has been projected as a fluorescent fibril sensor, and it has been claimed that AuO has an advantage over the most extensively utilized fibril marker, Thioflavin-T (ThT), owing to the presence of an additional large red-shifted emission band for AuO, which was observed exclusively for AuO in the presence of fibrillar media and not in protein or buffer media. As fibrils are very rich in β-sheet structure, a fibril sensor should be more specific toward the β-sheet structure so as to produce a large contrast between the fibril form and native protein form, for efficient detection and in vitro mechanistic studies of fibrillation. However, in this report, we show that AuO interacts significantly with the native form of bovine serum albumin (BSA), which is an all-α-helical protein and lacks the β-sheet structure, which are the hallmarks of a fibrillar structure.

Asn47 and Phe114 modulate the inner sphere reorganization energies of type zero copper proteins.

The geometric structures and electron transfer properties of type 1 Cu proteins are reasonably understood at the molecular level (E. I. Solomon and R.

Selective recognition of uranyl ions from bulk of thorium(iv) and lanthanide(iii) ions by tetraalkyl urea: a combined experimental and quantum chemical study.

The selective separation of uranyl ions from an aqueous solution is one of the most important criteria for sustainable nuclear energy production. We report herein a known, but unexplored extractant, tetraalkyl urea, which shows supreme selectivity for uranium in the presence of interfering thorium and other lanthanide ions from a nitric acid medium. The structural characterization of the uranyl complex (UO2X2·2L, where X = NO3(-), Cl(-) and Br(-)) by IR, NMR and single crystal X-ray diffraction provides insight into the strong interaction between the uranyl ion and the ligand.

Efficient Separation of Europium Over Americium Using Cucurbit-[5]-uril Supramolecule: A Relativistic DFT Based Investigation.

Achieving an efficient separation of chemically similar Am(3+)/Eu(3+) pair in high level liquid waste treatment is crucial for managing the long-term nuclear waste disposal issues. The use of sophisticated supramolecules in a rigid framework could be the next step toward solving the long-standing problem. Here, we have investigated the possibility of separating Am(3+)/Eu(3+) pair with cucurbit-[5]-uril (CB[5]), a macrocycle from the cucurbit-[n]-uril family, using relativistic density functional theory (DFT) based calculations.

Selectivity of a Singly Permeating Ion in Nonselective NaK Channel: Combined QM and MD Based Investigations.

Ion channels, such as potassium channels are known to discriminate ions to achieve remarkable selective transportation of K(+) over Na(+) through the membrane. The recently reported NaK ion channel, on the contrary, seems to be an exception, as it is observed to permeate most of the group IA alkali metal cations and hence is suggested to be nonselective in nature. However, does that correspond to a complete annihilation of selectivity inside the selectivity filter (SF) of the channel? What is the origin of such nonselectivity/selectivity, if any? The present computational study is an extensive multiscale modeling approach to find the probable answers to these intriguing questions.

Elucidating the structures and cooperative binding mechanism of cesium salts to the multitopic ion-pair receptor through density functional theory calculations.

Designing new and innovative receptors for the selective binding of radionuclides is central to nuclear waste management processes. Recently, a new multi-topic ion-pair receptor was reported which binds a variety of cesium salts. Due to the large size of the receptor, quantum chemical calculations on the full ion-pair receptors are restricted, thus the binding mechanisms are not well understood at the molecular level.

Water-Mediated Differential Binding of Strontium and Cesium Cations in Fulvic Acid.

The migration of potentially harmful radionuclides, such as cesium ((137)Cs) and strontium ((90)Sr), in soil is governed by the chemical and biological reactivity of soil components. Soil organic matter (SOM) that can be modeled through fulvic acid (FA) is known to alter the mobility of radionuclide cations, Cs(+) and Sr(2+). Shedding light on the possible interaction mechanisms at the atomic level of these two ions with FA is thus vital to explain their transport behavior and for the design of new ligands for the efficient extraction of radionuclides.

Effect of successive alkylation of N,N-dialkyl amides on the complexation behavior of uranium and thorium: solvent extraction, small angle neutron scattering, and computational studies.

The effect of successive alkylation of the Cα atom adjacent to the carbonyl group in N,N-dialkyl amides (i.e., di(2-ethylhexyl)acetamide (D2EHAA), di(2-ethylhexyl)propionamide (D2EHPRA), di(2-ethylhexyl)isobutyramide (D2EHIBA), and di(2-ethylhexyl)pivalamide (D2EHPVA)) on the extraction behavior of hexavalent uranium (U(VI)) and tetravalent thorium (Th(IV)) ions has been investigated.

Investigations on preferential Pu(IV) extraction over U(VI) by N,N-dihexyloctanamide versus tri-n-butyl phosphate: evidence through small angle neutron scattering and DFT studies.

Straight chain amide N,N-dihexyloctanamide (DHOA) has been found to be a promising alternative extractant to tri-n-butyl phosphate (TBP) for the reprocessing of irradiated uranium- and thorium-based fuels. Unlike TBP, DHOA displays preferential extraction of Pu(IV) over U(VI) at higher acidities (≥3 M HNO3) and poor extraction at lower acidities. Density functional theory (DFT) based calculations have been carried out on the structures and relative binding energies of U(VI) and Pu(IV) with the extractant molecules.

Modulation of protonation-deprotonation processes of 2-(4'-pyridyl)benzimidazole in its inclusion complexes with cyclodextrins.

2-(4'-Pyridyl)benzimidazole (4PBI) can exist in several states of protonation, having three basic nitrogen atoms. The equilibria involving these states, in ground as well as in excited states, are found to be affected significantly by cyclodextrins (CDs). The formation of inclusion complexes of this compound with all three varieties of cyclodextrins is observed to be more favorable at pH 9 than at pH 4, due to the predominance of the neutral form of dye at pH 9.